This invention relates to a vehicle height adjusting device, and more particularly to a vehicle height adjusting device equipped with a digital controller.
Conventional vehicle height adjusting devices perform an adjusting operation only while their ignition switch is in the conducting state, but it is convenient to maintain the adjusting operation for a certain period after the ignition switch is turned off in view of the getting on and off, loading and unloading, etc. For this reason, the vehicle height adjusting device incorporating a delay circuit has been proposed in Japanese Patent Unexamined Publication No. 99809/1981, for example. Now, it should be noted that the function of automatically cutting off the power supply after the ignition switch is turned off is called a self-cut-off function.
On the other hand, the adjusting devices have often employed a logic IC, microcomputer, etc. to implement their high performance. In the case where the above self-cut-off function is employed to maintain the adjusting operation of the adjusting device incorporating a digital controller for a certain period after the ignition switch is turned off and thereafter cut off the power source, i.e. to cut off the power supply to the circuits used, the supplied voltage is reduced with a certain time constant so that it passes the voltage not assured by IC itself, i.e. an uncertain voltage region, thus providing the possibility of making the device run away or making its self-cut-off function impossible. The occurrence of such a difficulty in the vehicle height adjusting device provides serious problems for vehicles since it leads to the overheat and burnout of a compressor motor, or the discharge of a battery which is due to the fact that the difficulty occurs after the turn-off of the ignition switch. The above self-cut-off function differs from the self-cut-off function used in the other houshold electric devices in that the operation of a control device must be stopped by the timer itself to prevent the battery from being discharged by the power consumption by the control device.